1. Field of the Invention
The invention relates to devices and techniques for coupling shafts and other portions of submersible pump assemblies and like components.
2. Description of the Related Art
Conventionally, electrical submersible pump (“ESP”) assemblies have been made up of a series of interconnectable modular sections including one or more pump sections with an associated fluid intake, a motor section and a seal section. Each of these sections includes an outer radial housing and a radially interior shaft. At present, the shafts and their connections are designed so that they can primarily transmit a compression load. The shaft of each section is interconnected with the shaft of the adjacent section by straight splining. There are normally no securing members used that would resist pulling apart of the shafts. Placement of the shafts or shaft connections under tension loads will cause the connection to separate easily.
This sort of “compression only” connection between shaft members is permissible when a standard ESP configuration is used wherein the pump section(s) are located above the seal and motor sections. Thrust bearings in the seal and motor sections support the pump sections, and the shaft members are not placed in tension. When a “bottom intake” ESP configuration is used, however, the pump section(s) are located below the motor and seal sections in the wellbore. An expensive thrust bearing is required to support the ESP components.
Although it might be possible to simply pin or weld the shafts of adjacent ESP sections together, there is an operational problem with doing so. In practice, it is difficult to assemble and disassemble the pinned shafts since they reside within the housings. If the connection is welded, it is quite difficult to disassemble the sections after removal of the pump assembly from the wellbore.
It would be desirable to have methods and devices that overcome the problems of the prior art.